Design and Experiment on One-octave Bandwidth Gyro-BWO with a Microwave Circuit in the Form of Zigzag Quasi-optical Transmission Line

The design and a proof-of-principle experiment on a gyrotron backward-wave oscillator (gyro-BWO) with broadband frequency tuning are discussed. The considered gyro-BWO uses a recently proposed interaction circuit in the form of a quasi-optical transmission line, where mirrors direct a Gaussian wave beam along a zigzag trajectory with vertical and inclined segments periodically spaced along the longitudinal z axis. The static B-field and the translational velocity of the electron are directed along z-axis, so that the electron beam periodically intersects with the wave beam. The resonant cyclotron beam-wave interaction occurs in the regions of perpendicular intersections of the beam and the wave, which leads to low sensitivity to the particle velocity spread, similar to the gyrotron. 3D PIC simulations show the prospects of this "zigzag" gyro-BWO in the implementation of frequency tunable generators capable of high power and unique (octave frequency band) tuning in the short millimeter wavelength range. The paper discusses the general layout and results of computer simulation a continuous-wave (CW) device using a cryomagnet with a B-field of 4–8 T. According to CST modeling, the gyro-BWO developed provides the output of a wave beam close to Gaussian with a power of near 1 kW at any given frequency in the range of 107–215 GHz. The cold-test results are in reasonable agreement with the simulations. The first results of the hot testing are expected by the time of the Conference.